FILE - In this Tuesday March 28, 2017 file photo, Britain's Prime Minister Theresa May, sitting below a painting of Britain's first Prime Minister Robert Walpole, signs the official letter to European Council President Donald Tusk, in 10 Downing Street, London, invoking Article 50 of the bloc's key treaty, the formal start of exit negotiations. Britons voted in June to leave the bloc after four decades of membership. (Christopher Furlong/Pool Photo via AP, File)
{}